IMO a bigger red flag would be poor record keeping on expenses and other documentation that would indicate property condition.Anyway, you're ultimately purchasing the income stream that *you* can achieve, not what the seller achieved.

A house in rural MO, like my mom's, doesn't require any permitting or zoning approval at all.

There were plenty of people not in a flood zone that wish they purchased flood insurance. 

As far as sourcing the lot, dealing with zoning or the city on new construction permits, engineering plans, etc. 

Although I would like to try to do it myself, crafting effective operating agreements is outside my comfort zone.

Understanding zoning, and land uses has been the extent of my experience. 

I help fund a large project out of the springs where it was bought prior to approvals but it was already properly zoned so it was just prosecuting the map under the given zoning and that still took a few years.

Hey, This is a unique situation, I purchased my second property in June 2024, a single-family home that used to be a duplex, and is still zoned as a duplex ( remains 2 addresses).

But, the situation you spelled out raises a lot of red flags. 

Duplexes can be a fantastic way to generate cash flow-just watch zoning laws, hire reliable contractors, and stay updated on rental trends.